Sulfurized/aminated mixture of ethylene-based polyolefin and polyisobutylene for lubricating oil

ABSTRACT

An effective amount of polyisobutylene effectively reduces polymerization and cross-linking reactions resulting in molecular weight and viscosity increase during production of dispersant viscosity index improvers by the amination and/or sulfurization of polyethylene containing polymers.

This invention relates to lubricating oil and lubricating oil additives.More particularly this invention relates to functionalized polymericadditives called dispersant viscosity index improvers which provide tolubricating oils dispersancy and viscosity index control at engineoperating temperature.

Dispersancy is the ability of an additive to disperse and suspend, in alubricant, dirt, insoluble combustion by products, etc. which otherwisewould form harmful deposits in the engine. Viscosity index controlprovides the lubricant with sufficient viscosity at engine operatingtemperature for efficient lubrication.

One class of dispersant viscosity index improvers is commonly preparedby functionalizing a polyolefin having viscosity index improvingproperties with polar reactants such as sulfur compounds and/or aminecompounds, etc. Dispersancy results from the presence of polar groupsformed from these polar reactants on the essentially nonpolaroil-soluble polymer. Deposit forming, essentially oil insolublecombustion by products are bound by the polar functional groups to theoil soluble polymer. Since the polymer is substantially oil soluble, theimpurities are suspended and held in the oil reducing formation ofharmful deposits on engine surfaces.

The high molecular weight and linear nature of the polyolefin producesviscosity index control in the lubricant. At ambient temperatures,lubricants have relatively high viscosity. At engine operatingtemperatures about 90°-200° C. (195°-395° F.), the lubricants tend tolose a substantial amount of viscosity. The addition of polymericviscosity index improvers increases high temperature viscosity. Atambient temperature polymeric viscosity improvers tend to be tightlycoiled into spherical bodies without substantial contribution toviscosity. As the temperature increases the polymer tends to uncoil andbecome extended in solution. This extended, more linear form increasesviscosity in proportion to the degree of extension. Thus as thetemperature increases the polymer contributes sufficient viscosity tothe oil to maintain adequate lubrication.

Often during amination or sulfurization, the molecular weight andviscosity of ethylene based polymeric additives containing polyethyleneunits, (--CH₂ CH₂ --)_(x), can increase by ten-fold or more. Thisviscosity and molecular weight increase results from cross-linking andpolymerization reactions caused by creation of reactive sites commonduring amination or sulfurization. This cross-linking, or polymerizationreaction resembles in some ways the vulcanization of rubber in whichlarge numbers of polymer molecules are linked by sulfide and polysulfidebonds. The viscosity increase can prevent further manufacturing of thecomposition since the high viscosity impedes filtering, pumping andblending. In the event that the viscous composition can be successfullymanufactured, the viscosity of the material is often too high to be usedin lubricants. At any engine temperature the lubricant would be toothick to be pumped through the engine, filtered, or provide adequatelubrication. The high molecular weight can also reduce the solubilityand the dispersancy of the additive in lubricating oil.

Thus, a need exists to control or limit cross-linking and the associatedmolecular weight and viscosity increase that is common duringsulfurization or amination of an amorphous ethylene based polyolefin.

A primary object of the invention is to improve the dispersant andviscosity index improving quality of functionalized polymeric sulfurizedor aminated lubricating oil additives. Another object of the inventionis to prevent undesirable molecular weight and viscosity increase duringmanufacture of aminated or sulfurized polyolefin dispersant viscosityindex improvers. Other objects appear herinafter.

I have discovered that the increase in molecular weight and viscosityobserved during the sulfurization and the amination of amorphousethylene based polyolefins containing a polyethylene units, (--CH₂ CH₂--)_(x), can be controlled by the addition of an effective amount of apolyisobutylene polymer. Apparently, polyisobutylene, containingrepeating units of fully substituted tertiary carbon atoms, when addedto ethylene based polymers reduces the tendency of the amorphousethylene based polyolefin to cross-link or polymerize during thesulfurization or amination reaction. The polyisobutylene apparently actsas a chain terminating agent which prevents substantial polymerizationor crosslinking and molecular weight increase by rapidly reacting withthe crosslinking or polymerizing active sites on the polymer, ending thereaction. The fully substituted carbon atoms of the polyisobutylene areunreactive in the cross-linking-polymerization reactions, and hence,tend to dilute the concentration of reactive cross-linking orpolymerization sites in the amorphous polymers. Since thepolyisobutylene can also act as a viscosity index improver, the additionof the polyisobutylene can provide added viscosity index control whilepreventing the unwanted viscosity and molecular weight increase.

Briefly, the dispersant viscosity index improving additives of thisinvention are prepared by the sulfurization and/or amination of amixture of a polyisobutylene polymer and a substantially amorphouspolymer comprising ethylene and at least one C₃₋₁₈ mono- orpolyunsaturated olefin. Commonly copolymers contain about 95-30 wt%ethylene and 5 to 70 wt% C₃₋₁₈ mono- or polyunsaturated olefinpreferably 35 to 45 wt% C₃₋₁₈ mono- or polyunsaturated olefin.Terpolymers contain about 90 to 30 wt% ethylene, about 10 to 70 wt%C₃₋₁₈ mono-olefin and about 1 to 30 wt% C₄₋₁₈ diolefin (C₄₋₁₈ conjugatedor C₅₋₁₈ nonconjugated diene).

The well-known copolymers and terpolymers of this invention subject tocross-linking comprise viscous or substantially atactic polymerscomprising ethylene, a C₃₋₁₈ olefin, and optionally, a C₄₋₁₈ conjugatedor C₅₋₁₈ nonconjugated diene. Examples of the C₃₋₁₈ olefin includepropylene (propene), 1-butene, 2-butene, isobutylene (2-methyl-propene),1-pentene, 2-hexene, 3-heptene, 4-methyl-2-pentene, t-decene,1-dodecene, 1-octadecene, etc. Representative examples of conjugateddiolefins (dienes) include butadiene, 1,3-hexadiene, 1,3-heptadiene,1,3-octadiene, 2,4-octadiene, 2,4-decadiene, branched acyclic dienessuch as 5-methyl-1,4-hexadiene, 3,7-dimethyl-1,7-octadiene, etc; andmultiring, cyclic, fused and bridged ring dienes such as cyclohexadiene,5-methylene-2-norbornene, 5-ethylidene-2-norbornene, etc.

These viscous polymers are well known in the art, and examples of thepolymers include ethylene-propylene copolymers, ethylene-octadecenecopolymers, ethylene-styrene copolymers, octadecene-styrene copolymer,ethylene-hexene-butadiene, terpolymers, ethylene-propylene-norborneneterpolymers, ethylene-propylene-5-ethylidene-2-norbornene terpolymers,ethylene-octadecene-5-ethylidene-2-norbornene terpolymers, etc. Thesecopolymers and terpolymers are produced by polymerizingolefinic-monomers in liquid or gas phase using aluminum chloride,sulfuric acid, acidic catalysts, and Ziegler-Natta catalysts etc. wellknown in the art comprising in addition, metal compounds of Groups IVB,VB and VIB of the Periodic Table, and organometallic reducing compoundsfrom Groups IIA, IIB, and IIIA. For example, VOCl₃ ; VO(AcAc)₂ ;VOCl(OBu), etc, in the presence of diethylenealuminum chloride,triisobutylaluminum, diethylaluminum chloride, etc.

The copolymers generally have a molecular weight of from about 600 to500,000, preferably 1,000 to 200,000, and most preferably 2,000 to100,000 to provide the high viscosity index control. These copolymersand terpolymers comprise essentially atactic or amorphous liquid orsemi-solid or non-crystalline polyolefins, but may contain up to 25percent by weight crystalline segments as determined by X-ray ordifferential scanning calorimetric methods. The polymers and copolymersof the invention can be degraded prior to reaction using oxidative ormechanical degradative methods. Mechanical degradation is used to adjustand control molecular weight and polydispersion (Mw/Mn) of the polymer.Oxidative degradation controls molecular weight and produces carbonyland other oxygen containing substituents on the polymer chain andassociated sites which can be functionalized with molar groups using avariety of reactions including the Mannich reaction with formaldehyde ora formaldehyde-yielding compound and an amine.

Polyisobutylene is a well-known amorphous polymer produced fromisobutylene containing streams derived from petroleum refineries whichcan contain other polymerizable hydrocarbons. Isobutylene monomer tendsto be highly reactive and polymerizes to the substantial exclusion ofother monomers. Polyisobutylene is commonly prepared by polymerizationof a petroleum stream in the presence of aluminum chloride or otheracidic catalysts. Molecular weights of the polyisobutylene commonlyrange from 200 to about 50,000. The polyisobutylene having a molecularweight from about 600 to about 10,000 and preferably about 900-5,000 isuseful in this invention in reducing cross-linking of the terpolymer andproviding added viscosity index improvement in the finished additivecomposition at low cost.

The amine reactant useful in the preparation of the lubricatingadditives of this invention includes primary and secondary aliphaticamines and polyamines having the formula NH₂ (CH₂)_(y) NH₂, wherein y isan integer of 3 to 12; polyalkylene polyamines of the general formulaNH₂ [(A--NH)]_(x) H wherein A is an alkylene unit having 2 to 6 carbonatoms and x is an integer from 2 to 10. Suitable amines includemethylamine, dibutylamine, cyclohexylamine, propylamine, decylamine,trimethylenediamine, hexamethylenediamine, ethylenediamine,diethylenetriamine, triethylenetetraamine, tetraethylenepentamine,tripropylenetetraamine, tetrapropylenepentamine, or mixtures thereof andother polyalkylene polyamines in which the alkylene group contains about12 carbon atoms. Other useful polyamines include N-amino-alkylmorpholine, 1,3-propane polyamines, polyoxy polyamines, bis(aminoalkyl)piperazine, bis(aminoalkyl) ethylene diamine, and bis(aminoalkyl)propylene diamine. Optionally, formaldehyde or formaldehyde yieldingreagents can be used to promote the amination reaction, including, forexample, formaldehyde, formalin, paraformaldehyde, trioxane, etc.

Sulfur or sulfur-yielding compounds include elemental sulfur, sulfurdichloride, sulfur monochloride, hydrogen sulfide, a phosphorous sulfidesuch as phosphorus pentasulfide (P₂ S₅), etc. Elemental sulfur in amolten or particulate form is preferred for reasons of reactivity andease of handling.

In somewhat greater detail, the additives of this invention can beprepared by sulfurizing and/or aminating a mixture of polyisobutyleneand an ethylene based viscous or substantially atactic polyolefinsubject to crosslinking.

Commonly, the polyolefin subject to cross-linking is blended with about0.1-20, preferably 1-6 moles of polyisobutylene per mole of ethylenebased polyolefin prior to amination or sulfurization for efficientprevention of viscosity and molecular weight increase. Thepolyisobutylene-polyolefin mixture can be dissolved in an inert solventsuch as hexane, heptane, lingroin, xylene, benzene, petroleum oilfractions, lubricating oil, kerosene, gasoline, etc., prior to thereaction.

The polymer-polyisobutylene can be reacted with from about 0.1 to about10 moles of sulfur compound per mole of polyisobutylene and polyolefincontained in the mixture, preferably from about 3 to about 5 moles ofsulfur can be added per mole of polyisobutylene and polyolefin.Sulfurization reactions can be promoted using a catalytic amount about0.001 to about 1 mole of catalyst per mole of sulfur. Catalysts comprisefree radical and acidic catalysts such as sulfur chlorides, peroxides,sulfonic acids, chlorine, etc.

The sulfurized polyolefin mixture can be aminated by contacting thesulfurized mixture with about 1.0 to 20 moles of amine per molepolyisobutylene and of pololefin. Preferably to attain a high proportionof amine functionality with reasonable consumption of amine about 2.0 to5.0 moles of amine per mole of polyisobutylene and polyolefin is used.

Sulfurized polyolefin mixture can be directly aminated. Sulfurizationproduces sulfur and non-sulfur containing active sites on the polyolefinchain reactive with amines and other reactants. Detail regarding thesulfurization and amination reactions can be found in U.S. Pat. Nos.3,459,664 and 3,364,232 which are expressly incorporated by referencehereto.

The sulfurized material is converted into a dispersant by means ofreaction with amine, optionally, to promote the amination, in thepresence of formaldehyde or a formaldehyde-yielding reagent. Thesulfurized olefin can be reacted with from about 0.5-10 moles of anamine per mole of olefin originally charged. The amination reaction iscommonly performed at a temperature between about 50°-400° C.,preferably a temperature of about 150°-200° C. for reasons of easereaction, and low degradation of products. While the reaction time isvariable depending on purity, concentration of ratio of reactants, thereaction is commonly complete at about 2-24 hours. Volatile andparticulate materials can be conveniently removed at this point. Theamination can be promoted by the presence of formaldehyde or aformaldehyde-yielding reagent. Formaldehyde also reacts with free aminogroups which often can be deposit precursors or corrosive in the engineinto non-corrosive dispersant moieties. Commonly, from about 0.5 toabout 10 moles of formaldehyde or formaldehyde-yielding compound can beadded per mole of amine. Preferably, from about 1 to 2.5 moles offormaldehyde or formaldehyde-yielding compound is added per mole ofamine for reasons of efficient reaction and low consumption ofreactants. The reaction of the amine, formaldehyde and thesulfurized-oxidized material can be conveniently monitored by observingthe 1720 CM⁻¹ band in the infrared (IR) spectra. The reaction can beconsidered essentially complete when the band has substantiallydisappeared.

Either ethylene based polymer, the polyisobutylene or mixtures thereofcan be mechanically or oxidatively degraded prior to reaction withsulfur and amine. Mechanical degradation is commonly performed inwell-known processes in apparatus, such as blenders or homogenizers,directing high shear forces on the polymer solution. The mechanicaldegradation reduces viscosity and molecular weight to desired level.Oxidative degradation is commonly performed by contacting the polymer insolution with oxidants such as oxygen containing gas to introducecarbonyl, aldehyde, hydroxyl and other oxygen containing groups into thepolymer chain. The oxygen containing groups produce active sites, oncarbon atoms alpha to the carbonyl or other oxygen containing group,that participate in a variety of reactions useful for production ofderivatives of the polymer.

Oxidatively degraded polymers commonly are aminated by reacting theoxidized polymer, formaldehyde or a formaldehyde-yielding compound andthe amine. This reaction is taught in Culbertson, U.S. Pat. No.3,872,019 and West, U.S. Pat. Nos. 4,011,380, and 4,131,553, which areexpressly incorporated by reference herein.

Both the sulfurization and amination reaction can produce greatquantities of tarry or charged byproducts which an contaminate theproduct and hinder filtration and other purification steps.

The removal of tarry byproducts of the olefin-sulfur-amine reaction canbe promoted by performing the amination or sulfurization reaction in thepresence of an alkali metal or an alkaline earth metal compound. About0.01-20 moles of the alkali metal or alkaline earth metal compound permole of amine can be added to the reaction mixture simultaneously withthe sulfur or sulfur-yielding compound or the amine. Sodium hydroxide,lithium chloride, potassium chloride, calcium oxide, calcium hydroxide,magnesium oxide, or magnesium hydroxide, barium hydroxide, calciumcarbonate, barium chloride, etc. can be added to the reaction mixture toreduce the tarry material. Apparently, the alkali metal or alkalineearth metal compounds react with or absorb the tarry reaction byproductsand reduce the sticky-tacky character or the tarry material. Thetarry-metal oxide product then precipitates and can be easily removed bywashing, filtration or centrifugation.

Commonly, the alkali metal or alkaline earth metal compound can be addedsimultaneously with the amine, prior to the amine, or after the amine.However, the best results are obtained when the alkaline earth metal isadded prior to or simultaneously with the amine compound.

Sulfurization and amination reactions can be conducted at a temperaturefrom about 50° C. to about 300° C. at atmospheric or superatmosphericpressure in an inert atmosphere or in ambient conditions. Commonly, thereactions take from about 30 minutes to about 24 hours, depending onconcentration, purity of reactants, and concentrations. At the end ofthe reaction, the reaction products are generally stripped with an inertgas to remove volatile materials and are commonly filtered to removeundesirable precipitates.

The additives can be made in batch or continuous operation. In batchoperation, the individual components are added to a suitable reactionvessel together or in discrete portions neat or dissolved in an inertsolvent. The components can be heated to control viscosity. Incontinuous operation, the reactant or reactants are added continuouslyto a horizontal or vertical reaction zone at appropriate feed rates indiluent or neat at temperatures to promote easy handling, reaction andsolubility.

The reaction products of this invention are effective lubricantcompositions when used in amounts of about 0.01 to 20 weight percentbased on the oil. Suitable lubricating base oils are mineral oils,petroleum oils, synthetic lubricating oils, and natural lubricating oilsof animal or vegetable origin. Concentrates of the additive inappropriate base oils containing greater than 10 weight percent areconvenient for producing finished lubricants at blending sites otherthan the manufacturing site of the additives. A variety of otheradditives can be used with the additive of this invention, includinganti-oxidants, dispersants, corrosion inhibitors, wear inhibitors,friction modifiers, detergents, anti-bacterial agents, etc.

The additives of this invention are evaluated using the Spot DispersancyTest. In the Spot Dispersancy Test, the ability of the additive in thelubricating oils to suspend and disperse engine sludge was tested. Toperform this test, to an amount of engine sludge produced in a VC or VDengine test is added about 15 wt.% based on the sludge of anexperimental additive to be tested. The sludge and additive areincubated in an oven at 146° C. for 24 hours. After this period, themixture is spotted on a clean white blotter paper. The oil diffusesthrough the blotter paper carrying the sludge to some extent, dependingon the dispersancy of the additive forming an oil diffusion ring and asludge diffusion ring. The dispersancy of the additive is measured bycomparing the ratio of the radius of the oil diffusion ring to theradius of the sludge diffusion ring. The diameter of the sludge ring isdivided by the diameter of the oil ring, and the result is multiplied by100 and is presented as a percent dispersancy. The higher the number,the better dispersant property of the additive.

The following examples and data are illustrative of methods for thepreparation and properties of the products of this invention. Theexamples should not be used to unduly limit the scope of the invention.

EXAMPLE I

Into a three-neck 1-liter reaction vessel equipped with a refluxcondenser, water trap, stirrer, nitrogen inlet tube, heater andthermostat was added 400 grams (0.01 moles) of a 10 wt. % solution ofethylene-propylene-5-ethylidene-2-norbornene terpolymer in 5 W oil and115 grams (0.05 moles) of a polyisobutylene polymer having a molecularwt. of about 2,300. The mixture was stirred and heated to a temperatureof 180° C. and 11.53 grams (0.36 moles) of sulfur were added. Theresulting mixture was stirred and heated to a temperature of 230° C. for5 hours to permit the sulfur to react. The mixture was stripped ofvolatile material for one hour with a stream of nitrogen at 2 cu. ft perhour. The mixture was cooled to 80° C. and 5.67 grams (0.28 moles) oftetraethylene pentamine, 10.0 grams (0.14 moles) of magnesium hydroxide,20 ml. of water, and 200 ml of xylene were added. The mixture wasstirred and heated to a temperature of 165° C. for five hours. Duringthis period water was removed azeotropically. The mixture was cooled,diluted with heptane and filtered. Hexane and other volatiles wereremoved with a stream of nitrogen at 235° C. Viscosity of the mixture at210° F. was 10.84 Cst.

EXAMPLE II

Into a 1 liter, three-neck flask equipped with a reflux condenser,stirrer, nitrogen inlet tube, heater and thermostat was charged 250grams (0.067 moles) of a 10 wt. % solution ofethylene-propylene-5-ethylidene-2-norbornene terpolymer in 5 W oil and1.5 grams (0.046 moles) sulfur. The mixture was stirred and heated to atemperature of 225° C. until the evolution of H₂ S ceased (about 2.5hours. The mixture was cooled to 100° C. and 2.5 grams (0.13 moles) oftetraethylene pentamine was added. The mixture was stirred and heated toa temperature of 190° C. until H₂ S evolution again ceased (about 0.5hours). About 5.0 grams (0.07 moles) of calcium hydroxide was added andthe mixture was stirred and heated to a temperature of 190° C. for 1hour. The product was filtered through Celite. The product was tooviscous to measure viscosity.

EXAMPLE III

Thirteen hundred twenty (1320) grams of an ethylene, propylene,5-ethylidene-2-norbornene terpolymer (Mn=35,000, Mw=175,000) wasdissolved in 13,200 grams of SX-5 W oil at 180° C. Three hundred forty(340) grams of polyisobutylene (Mn=2,024) were added. The solution wascooled to about 100° C. and about 15 liters of heptane were added.Twenty milliliters of tertiary C12 mercaptan were added to the solutionand the polymers were passed through a Gaulin mechanical homogenizeruntil the viscosity of the solution was about 3,069 SUS at 210° F.Heptane was removed from the solution by distillation at 100° C. undernitrogen. The solution contained 7.54 percent sheared terpolymer, 73.67percent oil, and 18.97 percent polyisobutylene.

To 1000 gms of the product prepared above in a three-neck 1-literreaction vessel equipped with a reflux condenser, water trap, stirrer,nitrogen inlet tube, heater and thermostat were maintained at 180° C.,were added 19.82 grams (0.62 moles) sulfur. The solution was mixed andthe temperature was raised to 235° C. for five hours and H₂ S evolutionwas measured. At five hours reaction time, 2.0 cubic feet of nitrogenper hour was passed through the solution at 235° C. to remove volatiles.The solution was cooled to 80° C. and 80 milliliters of xylene, 11.47grams (0.06 moles) of tetraethylenepentaamine, 20 grams (0.34 moles) ofmagnesium hydroxide, and 20 milliliters of water were added to thesolution. The water was slowly removed azeotropically and the solutionwas held at 165° C. for five hours. The solution was diluted with anequal volume of xylene and filtered. To the filtrate, stripped ofvolatile material, including xylene and water, was added 3.75 grams(0.06 moles) of boric acid and 19.7 grams (0.24 moles) of 37 weightpercent formaldehyde solution. The resulting solution was stirred at 80°C. for 30 minutes and water and solvent were again removed at 175° C.with a stream of nitrogen.

                  TABLE I                                                         ______________________________________                                        VISCOSITY OF PRODUCTS                                                                     @ 210° F. (SSU)                                            ______________________________________                                        EXAMPLE I     10.87                                                           EXAMPLE II    Too viscous to measure                                          ______________________________________                                    

                  TABLE II                                                        ______________________________________                                        SPOT DISPERSANCY TEST                                                                         % Dispersancy                                                 ______________________________________                                        EXAMPLE III       91.0                                                        Commercial Dispersant                                                                           91.0                                                        Viscosity index improver                                                      ______________________________________                                    

An examination of Table I of data shows that the viscosity of theproduct of Example II, prepared from anethylene-propylene-5-ethylidene-2-norbornene terpolymer, is too viscousto measure, and too viscous to be useful in a lubricant. The product ofExample I, prepared from a mixture of theethylene-propylene-5-ethylidene-2-norbornene terpolymer andpolyisobutylene polymer, however, has a viscosity suitable for use in afinished lubricant. In Table II the product of Example III has anexcellent dispersancy when compared to a commercial dispersant viscosityindex improver.

The foregoing specification and examples are illustrative of theinvention. Since many embodiments of the invention can be made, theinvention resides solely in the claims hereinafter appended.

I claim:
 1. A lubricating oil which comprises a major portion of alubricating base oil and about 0.01 to 20 wt.% based on the lubricatingoil of a dispersant viscosity index improper resistant to viscosity andmolecular weight increase during production, which comprises thereaction product of an amine, sulfur or a sulfur-yielding compound and amixture of polyisobutylene and a substantially amorphous polymercomprising ethylene and at least one monomer selected from the groupconsisting of a C₃₋₁₈ olefin, and a C₄₋₁₈ diene.